In the course of studies directed toward to the stereo-controlled synthesis of substituted decahydro-quinolines, a method of producing trans-N-acyl-N-alkyl-1-amino-1,3-butadienes was required. However, the readily apparent processes did not yield the desired compounds. Thus U.S. Pat. No. 2,446,172 teaches that N-alkyl-2-aminobutene-3-when heated and then contacted with an acylating agent, possibly in the presence of a catalyst, yields N-alkyl-N-acyl-2-amino-1,3-butadienes. However, direct acylation of N-alkyl-1-imino-2-butenes, which are readily prepared from crotonaldehyde and primary amines, with carboxylic acid anhydrides and/or acid halides in the presence of triethylamine or sodium acetate failed to give the desired dienamides. Under these conditions, the non-conjugated azomethines were effectively converted to N-acyl-enamines.
Accordingly, it is the object of this invention to provide novel trans-N-acyl-N-alkyl-1-amino-1,3-butadiens and a method by which they may be prepared. This and other objects of the invention will become apparent to those skilled in the art from the following detailed description.